The main objective is to determine compositional and structural details of the inorganic phase in teeth and bones. Infrared (4000-60 cm-1) and Raman spectroscopy as well as chemical methods are employed in these studies. Methods are devised for preparation of synthetic calcium apatites of controlled physical properties (crystal size and perfection) and chemical composition containing biologically relevant constituents, e.g., hydroxyl, fluoride, chloride, carbonate, water and acid phosphate. The vibrational spectra of these apatites and related compounds are assigned and characterized. Isotopically enriched apatite analogs are prepared to facilitate spectral assignments. The spectroscopic assignments and supplemental spectral data (temperature dependency and polarization) are utilized to establish compositional and structural details of the apatites which include the type and geometry of ions, the site or number of sites occupied by ions, orientation of ions, chemical bonding and interactions of ions and semiquantitative estimations of constituents present. The results of findings for the controlled apatite system are related to the inorganic phase in calcified tissues.